Melt formable tetrafluoroethylene/fluoroalkoxy trifluoroethylene copolymers (known by the acronym PFA) have excellent characteristics in heat resistance, chemical resistance, and the like, and are used to obtain bottles and tubes by melt extrusion, which find use in containers for high-purity chemicals used in semiconductor manufacture or tubing for transporting liquid chemicals or ultra-pure water.
The problem has arisen in semiconductor-related applications, that articles extruded from PFA do not have smooth surfaces, so that contaminants in the liquid chemicals used in these applications tend to adhere to the surface, and are difficult to remove even upon rinsing.
The reason the surfaces of the PFA-extruded products are not smooth is that coarse spherulites, reaching diameters of 20-150 micrometer (.mu.m), are generated during the crystallization of PFA, with their spherulite border regions generating deep grooves on the surface of the molded products. It is generally known that the size of a spherulite can be made smaller by increasing the number of spherulite nuclei. A variety of inorganic or organic crystallization nucleating agents have been added to crystalline resins for this purpose. Nucleating agents for rendering finer spherulites in fluororesins have also been proposed, which include metal sulfate salts for polychlorotrifluoroethylene (Japanese Patent Application Publication Kokai 49-5153) and alkali metal salts for polyvinylidene fluoride (Japanese Patent Application Publication 49-17015) However, in semiconductor manufacturing process-related applications which require particularly high purity liquid chemicals or ultra-pure water, metal salt nucleating agents will leach out, causing contamination in the process steps and adversely affecting PFA's chemical resistance and minimal contamination advantages.